Trigonometry is based on triangles.

Here is a little diagram.
[img]http://www.swiftless.cdadc.com/trig.jpg[/img]

Now:
O stands for opposite.
A stands for adjacent.
H stands for hypotenuse.
alpha is the angle in the corner where alpha is located.

Ok, now the 3 trigonomic functions are:
sine, cosine and tangent

these will be known as:
sin, cos and tan on your calculator.

here I am going to let alpha be @ as I dont have any alpha key to press  :P 
so to remind you alpha is our angle, so @ will be known now as our angle.

now the 
sin@ = o/h
cos@ = a/h
tan@ = o/a

you can easily remember this by a little saying:
soh cah toa

So why do we need this? We need this when we want to find the length of a side in a triangle. If you have the A and the @, then you can use trigonometry to find either H or O.

Next we can use trigonometry to find the unknown angle.

to do this, you start with your basic formula, eg:
sin@ = o/h

then we have to get sin on the other side, so we times both sides by the opposite
of sine which is sin^-1, which should also be on your calculator.

so by doing this we end up with:

@ = sin^-1(o/h)

And that is all there is to trigonometry. You can find sides and angles.

[img]http://www.swiftless.cdadc.com/trig2.jpg[/img]

In the image above it shows you a rough idea of how you would make this into a camera for a game. You have yourself in the centre and have 360 degrees of rotation around. You can use trigonometry, and with your current angle, and knowing your current position to A(where you wish to go) you can determine your point at the corner of H and O.

But that is just a quick reference I whipped up in 10 minutes.

If you have any questions, then just post here.